Oliver Hartmann (born June 28, 1970 in Rüsselsheim) is a German metal vocalist, guitarist, songwriter, and producer who performed in various acts, either as guitarist, solo or choir singer. He is best known for his role as founder of the band At Vance (together with Olaf Lenk), his current band Hartmann and his guest appearances on albums of several prominent metal bands, including Freedom Call, Edguy, Rhapsody, Genius rock opera, Iron Mask, Aina's metal opera Days of Rising Doom and the metal opera Avantasia where he participated as a vocalist in 4 albums and also as a guitarist of the live and studio line up. He is also guitarist and vocalist with the Pink-Floyd tribute band Echoes.

Hartmann began his career as guitarist in several local bands but since the age of 18 concentrated more on his singing. Among others he played in bands as Hanz Damf, Tuned, and Centers, the latter with which he made his first international appearances. He reached his first success with At Vance, in which he sang from 1999 to 2002. Since leaving At Vance on personal reasons, he concentrated mostly on his solo career and on studio recording. So far he has recorded four solo albums, Out in the Cold, which was released in 2005 on the Italian Frontiers Records label, on which he also plays guitars, Home, which was released in early 2007, the live acoustic DVD/CD Handmade and the latest release 3 in late 2009. Hartmann currently also sings in Italian band Empty Tremor, which was a support act for Dream Theater during a 2004 tour in Italy. With his band, Hartmann he also supported TOTO during their European tour 2006, House of Lords and The Hooters in 2007. During the past two years, the band HARTMANN played numerous festivals and shows as support of bands such as MOTHER’S FINEST, URIAH HEEP and Y&T.